ABSTRACT ? MOUSE HISTOLOGY AND PHENOTYPING LABORATORY The Mouse Histology and Phenotyping Laboratory (MHPL) was originally established in 2009 as a developing core laboratory for the Lurie Cancer Center (LCC), and emerged as an established core after the last competing CCSG renewal in 2013. The core provides LCC members and the Northwestern University (NU) research community with histopathologic assessment of experimental research animal tissues by trained pathologists and expert histotechnologists. The mission of MHPL is to provide investigators with highly specialized tissue-based histology and phenotyping services to support their animal-based research work. Since the last competing renewal, the laboratory has expanded its services and now provides comprehensive histology services for a wide variety of research animal species. Phenotyping services include immunohistochemistry (IHC), immunofluorescence (IF), whole mouse necropsy with detailed phenotyping of organs and tissues, and tissue- based toxicology analyses. The laboratory also provides training opportunities for students, post-doctoral fellows, staff and research faculty to learn histology and phenotyping analysis techniques. The MHPL Director is a board- certified pathologist and is available to assist LLC investigators in developing the best strategies to elucidate specific phenotypes, gain mechanistic insights regarding the biologic actions of targeted molecules, and study the toxicity and/or therapeutic efficacy of exogenously administered substances in rodents. The comprehensive histopathology support services provided by the MHPL enhance the ability of LCC investigators to characterize viable and embryonic lethal mouse models, and to develop and analyze new in vivo model systems for studies of cancer biology, prevention, and therapy. The use of the MHPL by LCC members has increased substantially over the current funding period. During the last year, the core provided services to 74 LCC members, of which 69 were peer review funded and whose work resulted in multiple high impact publications.